Hi Rita - here are a few links you might find helpful.
UCD prospective students: http://www.ucd.ie/newstudent/
A list of all postgrad courses at UCD: http://www.ucd.ie/~pgstudy/listing.htm
Architectural postgrads in particular are at:
The postgrad studies office: http://www.ucd.ie/~pgstudy/
Faculty of Engineering and Architecture: http://www.ucd.ie/~engineer/
International office: http://www.ucd.ie/~global/
Hope you find what you're looking for!